The present invention relates generally to a method of controlling the tension in a plurality of yarns during delivery in the form of a sheet for winding about a suitable winding core, e.g., in the preparation of a warp beam or the like.
In the preparation of warp beams and the like, a plurality of textile yarns are transported in side-by-side, generally parallel relation in the form of a sheet successively via a pair of driven delivery rollers, peripherally about a movable dancer roller and onto a driven winding core, such as a warp beam. A desired level of tension in the yarn sheet is obtained by biasing the dancer roller, e.g. pneumatically, into peripheral engagement with the traveling yarn sheet while at the same time driving the pair of delivery rollers and the warp beam at differential peripheral speeds. As will be understood, as the yarn sheet is progressively wound about the warp beam, the effective diameter of the beam gradually increases which, in turn, necessitates a gradual reduction in the driven axial speed of the warp beam to maintain a constant peripheral speed of the beam for yarn take-up. Typically, the driven speed of the warp beam is suitably controlled over the course of the winding operation according to a predetermined program stored in a suitable programmable controller.
While the dancer roller is supported so as to be movable in response to tension fluctuations in the yarn sheet during the winding operation, it is preferred that the yarn sheet tension be maintained as constant as possible so that the dancer roller is maintained generally stationary in static equilibrium at a predetermined desired residence position and does not move substantially therefrom. Thus, during winding operation, the dancer roller may move in response to tension fluctuations by only minimal amounts on the order of at most 1 centimeter from its static residence position. Accordingly, the tension-responsive movements of the dancer roller do not provide a suitable reference for making basic corrections or for providing the primary control of adjustments in the driven speed of the warp beam or other winding core in relation to the traveling speed of the yarn sheet as determined by the driven speed of the delivery rollers.